Engine construction



Jan. 14, 1969 A, WISEMAN 3,421,490

ENGINE couswnucmou Filed July 10, 1967 Sheet of :5

FIG. I

ATTORNEYS Jan. 14, 1969 w. A, WISEMAN 3,421,490

ENGINE CONSTRUCTION Filed July 10, 1967 Sheet 2 Of 5 I Q o O a \QQ a \5 O 0 I o L [I mvzu'ron WILL/HM r4. w/5EM/M ATTORNEYS Jan. 14, 1969 w. A. WISEMAN 3,421,490

ENGINE CONSTRUCTION Filed July 10, 1967 Sheet 3 of 5 INVENTOR U /LL/A'M l4 M/SEMflA/ ATTORNEYS United States Patent Oflice 3,421,490 Patented Jan. 14, 1969 Claims ABSTRACT OF THE DISCLOSURE A horizontally opposed engine component arrangement incorporating a longitudinally split crankcase, each crankcase half internally supporting a forward reduction gear section, a center power section, and a rear accessory section drivably connected to sideward extending accessories. All accessories are integrally mounted to the crankcase IO eliminate external connections.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to internal combustion engines and more particularly to a forward reduction gear train, an intermediate power section and a rear accessory gear train all mounted within a split crankcase having surfaces mating in a vertical plane passing through the axis of rotation of the crankshaft.

Description of the prior art Internal combustion engine manufacturers have directed considerable effort toward developing a low cost, light weight engine which can develop a high power output While at the same time providing a smooth and quiet operation. In general these efforts have taken the form of developing a relatively large displacement engine having expensive and sophisticated cylinders in order to achieve the required horsepower. This approach has necessarily produced a compromise in achieving a high horsepower engine in a light weight package.

A factor contributing to the overall weight of conventional engines has been the crankcase configuration. A typical engine of the prior art employs a crankcase for housing the crankshaft and the engine cylinders, a separate housing attached to the crankcase for supporting the reduction gear train connecting the output of the crankshaft to a driven member such as a propeller shaft or the like, and still another housing attached to the crankcase for supporting an accessory gear train for providing power for various accessory components which are essential to the operation of the engine such as the magnetos and the like.

The broad purpose of the present invention is to provide a basic engine arrangement for a family of engines which provides a maximum interchangeability of components to achieve major cost reductions. The basic engine arrangement achieves a higher horsepower in a light weight package as the result of the reduced number of components and a novel form of crankcase for housing the crankshaft, the reduction gear train and the accessory gear train which reduces the conventional multi-housing arrangement to a single housing.

SUMMARY The preferred engine achieves a high horsepower, low weight configuration through a small displacement, high crankshaft speed combination. The crankshaft speeds are higher than have been used in aircraft engines of this type in the prior art and contemplates speeds up to 4 to 5 thousand rpm. In order to accommodate this high crankshaft rpm, the preferred engine employs a camshaft that rotates at one-half the crankshaft speed which is a compatible propeller speed. By coupling the propeller shaft directly to the camshaft, the crankshaft rotation can be reduced through a common reduction gear set to a speed compatible to both elements.

Another feature of the preferred engine which makes it possible to achieve essentially a one horsepower per pound weight ratio is a novel form of hydraulic coupling connecting the output of the crankshaft to the propeller shaft. This novel coupling was disclosed in our co-pending patent application, Ser. No. 569,489 filed Aug. 1, 1966 and eliminates the conventional type of pendulum damper that is often required in quantities as high as six per engine on a six cylinder engine. These conventional pendulum dampers are expensive, heavy, intricate, and add as many as 102 separate parts to the crankshaft in order to control the vibration of the engine.

To achieve substantially interchangeability of parts in a family of engines of four, six, and eight cylinders the basic components are designed so that the tooling is interchangeable between different size engines.

The preferred embodiment of the present invention takes the form of a horizontal, opposed cylinder construction employing a two-piece crankcase that is split along its longitudinal axis and center-bolted together. The preferred crankcase incorporates an intermediate power section for mounting the cylinders, an accessory section at the rear for mounting the accessories and houses the full reduction gearing for the propeller shaft at its forward end. All three of these basic components are mounted to the two split crankcase halves. This differs substantially from conventional engines which have a separate power section, a separate machine attached to the accessory section at the rearward end of the crankcase and a separate propeller reduction section attached to the front of the engine.

The 'basic engine arrangement provides a basic engine construction for a family of engines so that the primary differences between a 4, 6, or 8-cylinder engine are a longer camshaft, a longer crankshaft and a longer crankcase for housing the crankshaft and the camshaft. All other major components are completely interchangeable such as the hydraulic coupling, the cylinders, the valves, the gears and the like.

The basic crankcase permits all the accessories to be directly mounted on the crankcase so that there are no external lines on the engine.

The major contribution of the preferred engine construction is the reduced weight per horsepower. Thus, a light weight, high horsepower unit is feasible wherein a 4-cylinder version has a little over 1 pound per horsepower ratio and the 6 and 8 cylinder versions drop below the 1 pound per horsepower ratio. This compares to a conventional aircraft engine weight to power ratios that are about 2 pounds plus per horsepower in the low horsepower range and in the higher horsepower range, drop down to about 1 /2 pounds per horsepower. The typical 8 cylinder engine embodying the present invention develops 400 horsepower with a weight of about 357 pounds.

It is therefore an object of the present invention to provide a high horsepower, light weight engine configuration having a crankcase for housing the crankshaft, a forward reduction gear, and a rear accessory drive train.

It is another object of the present invention to reduce the weight of internal combustion engine assemblies by providing a crankcase for directy mounting the cylinders, the accessories, and the reduction gearing so that all external connections are eliminated.

It is still another object of the invention to reduce the Weight of internal combustion aircraft engines by providing a crankcase for housing the crankshaft and the gear trains associated with the propeller shaft and the accessory components and comprising a pair of longitudinally split crankcase halves.

It is a still further object of the present invention to provide a basic engine construction for a family of engines whch permits a maximum intercchangeability of components and tooling between engines of different sizes.

Still further objects and advantages of the present invention will readily occur to one skilled in the art to which the invention pertains upon reference to the following detailed description.

DESCRIPTION OF THE DRAWINGS The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views and in which:

FIG. 1 is a plan view of a 4-cylinder aircraft engine illustrating a preferred embodiment of the present invention;

FIG. 2 is a side view of the preferred engine illustrated in FIG. 1;

FIG. 3 is a side view of a six-cylinder engine illustrating another embodiment of the present invention;

FIG. 4 is an enlarged longitudinal sectional view through the engine of FIG. 1;

FIG. 5 is a transverse sectional view of the engine of FIG. 1 looking forward from the rear end thereof and;

FIG. 6 is an enlarged transverse sectional view through one of the opposed cylinders of the engine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawings, a preferred engine 10 is illustrated in FIGS. 1 and 2 as having a pair of horizontally opposed banks of cylinders 12 and 14, each bank consisting of two cylinders. The banks 12 and 14 are mounted on a crankcase 16 which also provides means for mounting a starting motor 18, an intake manifold 20, an exhaust manifold 22 and a muffler 24.

The engine 10 is shown as being housed within an aircraft nacelle 26 to illustrate the compact arrangement of the engine components. It is to be understood, however, that the preferred engine can be employed as a source of power in a variety of applications other than in an aircraft power plant.

A propeller shaft 28 adapted to carry a conventional propeller (not shown) is coupled to the output of the cylinder banks 12 and 14. The conventional accessories are mounted at 30 and 32 to the rear part of the crankcase 16 and extend sideways to reduce the overall length of the engine. The accessories are mounted directly to the crankcase 16 so that there is a complete absence of external connections or the like which are typical of conventional engines.

Now referring to FIGS. 4 and 6., the preferred crankcase 16 comprises a pair of crankcase halves 34 and 36 bolted together by threaded fasteners 38 along a vertical longitudinal plane. Each crankcase half supports a cylinder bank so that the cylinder banks 12 and 14 are arranged in horizontally opposed relationship.

A typical cylinder assembly 40 is illustrated in FIG. 6 as being mounted in the crankcase half 36. A cylinder 41 and head 42 form a combustion chamber. A piston 44 reciprocally mounted within the cylinder 41 is connected by an arm 46 which in turn is pivotally connected to a crankpin 48 which forms a part of a crankshaft 50. The crankshaft 50 is mounted by longitudinally spaced bearing means 52, 53 and 54 for rotation within the crankcase 16. The bearing means 52, 53 and 54 are supported by each of the crankcase halves 34 and 36 so that the crankshaft 50 rotates about an axis in the vertical plane in which the two crankcase halves 34 and 36 are joined together.

Thus the reciprocating motion of the piston 44 is converted into rotational motion of the crankshaft 50.

As best seen in FIG. 6, an overhead camshaft 58 is mounted by bearing means 60, 62 and 64 to the crankcase halves 34 and 36. The camshaft 58 is supported for rotation about an axis parallel to the axis of rotation of the crankshaft 50 and is also arranged in the same vertical plane in which the two crankcase halves 34 and 36 are joined together.

The camshaft 58 has cam surfaces 66 each of which is engaged with a tappet assembly 68, pushrod 70, and rocker arm assembly 72 to open and close a valve assembly 74 associated with each of the cylinders in a timed relationship with the rotation of the crankshaft 50 in the manner well known to those skilled in the art. The engine 10 is of the 4-cycle type with the cylinders going through a firing sequence in a timed progression with an intake valve admitting a combustible mixture to each combustion chamber for ignition by a sparkplug 76 to create a power stroke with the products of combustion exhausting through an exhaust valve at the end of the power stroke.

Now referring back to FIG. 4, the rearward end of the camshaft 58 is connected to a tachometer drive member 76. The forward end of the camshaft 58 is coupled directly to the propeller shaft 28 by a coupling member 78 so that the propeller shaft 28 and the camshaft 58 rotate together about a common axis.

The crankshaft 50 is connected through a hydraulic coupling assembly 80 to a quill shaft 82 which is also mounted within the crankcase halves 34 and 36 and extends forwardly from the crankshaft 50. The hydraulic coupling 80 is described in detail in my aforementioned co-pending application and provides a vibration absorbing coupling between the crankshaft 50 and the quill shaft 82. The shaft 82 has a gear 84 meshing with a gear 86 carried by the propeller shaft 28 so that the quill shaft 82 is drivingly coupled with .e propeller shaft 28. The gears 84 and 86 provide a speed reduction means so that the high output of speed of the crankshaft 50 is reduced to a compatible speed for the propeller shaft 28. This reduction is preferably -a 2 to 1 ratio so that when the crankshaft 50 is being driven at 4,000 rpm. the camshaft 58 and the propeller shaft 28 are driven at 2,000 rpm. This novel gear reduction arrangement provides means for reducing the output of the crankshaft through a single pair of gears to -a speed accommodating both the propeller shaft 28 and the camshaft 58.

The starter motor 18 is mounted to the crankcase half 36 and is coupled to a clutch assembly 88 connected to the quill shaft 82.

It is to be understood that the entire reduction gear assembly connecting the output of the crankshaft 50 to the propeller shaft 28 is mounted within the split crankcase halves 34 and 36. This compact arrangement is made possible as a result of a number of novel features of the preferred engine including the absence of the conventional pendulum vibration dampers which are a necessary part of conventional engines and which are eliminated by the novel hydraulic coupling assembly 80.

As best seen in FIGS. 4 and 5, an accessory gear train 90 comprising a bevel gear 92 carried at the extreme rearward end of the crankshaft 50 is in mesh with :a second bevel gear 94 which is carried by an accessory drive shaft 96. The shaft 96 is supported at right angles to the crankshaft 50 by bearing means 98 and 100 mounted within the crankcase halves 36 and 34 respectively. The accessory drive shaft 96 provides means for driving sidewardly extending accessories such as an oil pump 102 which is mounted to the crankcase half 34 and a fuel pump 104 which is mounted to the crankcase half 36.

An intermediate shaft 106 journalled in bearing means 108 and 110 which are mounted in the crankcase halves 34 and 36 is supported for rotation in spaced parallel relationship above the drive shaft 96 and is driven by the shaft 96 through a pair of gears 112 and 114. The shaft 106 provides means for driving a second pair of side mounted components such as the engine magnetos not shown) and the like. An upper shaft 116 is journalled in bearing means 118 and 120 Within the crankcase halves 34 and 36 and is coupled by gear 124 to the gear 114 carried by shaft 106. This arrangement wherein the accessories are each side mounted to the crankcase 16 and at the rear end thereof reduces the overall length of the engine and in addition eliminates all exterior connections between the crankcase and the accessories.

FIG. 3 shows a 6-cylinder engine 130 illustrating another embodiment of the invention. Engine 130 includes a crankcase 132. Cylinders 134 mounted on the crankcase 132, intake manifold 136, exhaust manifold 138 and turbocharger 140 also mounted on the crankcase 132. The crankcase 132 is also split down the middle to form a pair of halves with a propeller shaft 142 coupled to the cylinders 134 and side-mounted accessory units 144 and 146 and 148 attached to the rear of the crankcase 130. The G-cylinder engine 130 illustrates how a family of engines incorporating the basic arrangement of components is available so that the advantages of interchangeable tooling can be fully realized. Thus the 4-cylinder engine differs from the 6-cylinder engine 130 essentially in that the engine 130 has a longer camshaft, a longer crankshaft :and a longer crankcase to accommodate the greater number of cylinders. The remaining components, such as the cylinders, the valves, accessories, gear trains and the like remain the same between engines. A similar result occurs by incorporating the basic construction of the present invention in an S-cylinder engine arrangement.

Thus a high horsepower, low weight engine can be produced by housing the crankshaft and the gear trains Within a split crankcase and by mounting the accessories directly to the crankcase to reduce external connections. In addition, the novel gear and coupling arrangements reduce the overall number of components which in turn provide added weight and cost reductions.

Although I have described two embodiments of my invention, it is to be understood that the basic engine arrangement disclosed herein can be adapted to multicylinder engine employed in a wide variety of applications other than for aircraft.

Having described my invention, I claim:

1. In an internal combusion engine having a crankshaft coupled to a driving piston, !3. gear assembly connecting said crankshaft to a driven output shaft, a camshaft driven by said crankshaft, and an accessory gear train connecting said crankshaft to an accessory unit,

(a) a crankcase for carrying said crankshaft, said piston, said gear assembly, said output shaft, said accessory gear train and said accessory unit,

(b) said crankcase comprising a pair of halves joined to one another in a plane passing through the axes of rotation of said crankshaft, said camshaft and said output shaft and including bearing means carried by each of said halves for rotatably supporting said crankshaft, said camshaft and said output shaft,

(c) said accessory unit comprising a plurality of accessory drive shafts extending at right angles with respect to the axes of said crankshaft, and

(d) said crankcase halves each rotatably supporting opposite ends of said accessory drive shafts whereby all of said shafts are supported jointly by said crankcase halves and upon separation of said crankcase halves said crankshaft, said camshaft, said output shaft and said accessory shafts are removed from supporting engagement from at least one of said halves.

2. The engine as defined in claim land including means provided on the exterior surfaces of said crankcase halves for supporting accessories and for connecting said accessories with said accessory shafts.

3. The engine as defined in claim 1 and in which each of said halves is integral in construction.

4. The invention as defined in claim 1, including a pair of horizontally opposed banks of cylinders, each of said banks of cylinders being associated with one of said crankcase halves.

5. The invention as defined in claim 1, including a pair of horizontally opposed banks of cylinders arranged on opposite sides of said plane.

6. The invention as defined in claim 1, wherein said cylinders are arranged on each side of said crankshaft in opposed banks each consisting of tWo cylinders.

References Cited UNITED STATES PATENTS 1,676,418 7/1928 Vincent 123195 2,001,866 5/1935 Carninez 123-195 2,021,262 11/1935 Moore 123-56 2,550,696 5/1951 Hiss 12355 XR 2,678,037 5/1954 Wiegman et al 123195 2,968,293 1/1961 Kolbe 12356 XR 3,073,291 1/1963 Leonard et al l23195 FOREIGN PATENTS 943,293 12/ 1963 Great Britain.

WENDELL E. BURNS, Primary Examiner.

US. Cl. X.R. l2355, 56 

